When the Large Hadron Collider (LHC) began operating in 2008, the goal seemed almost unattainable: recreate for an infinitesimal fraction of a second the conditions that existed just after the Big Bang. Four years later came the discovery of the Higgs boson, one of the greatest feats of modern physics.
Since then, the accelerator has produced billions of proton collisions, made it possible to study nature’s fundamental particles with unprecedented precision, and searched, so far without success, for signs of new physics beyond the Standard Model. Now, after almost two decades of operation and three campaigns of experiments, The largest scientific instrument ever built has just gone dark. But not because he has finished his mission. Quite the opposite.
CERN has begun a technical shutdown that will last until 2030 to transform the LHC into a much more powerful machine: the High-Luminosity Large Hadron Collider (High-Luminosity LHC or HL-LHC). It will not be more energetic but much more productive. When talking about a particle accelerator, it is common to think that the improvement consists of increasing the energy of the collisions. In this case something different happens. The HL-LHC will maintain practically the same maximum energy (13.6 teraelectronvolts), but will dramatically multiply the number of collisions it produces. The key is in a concept called luminosity.
Basically, instead of making a more powerful camera, they will take a lot more pictures. Thanks to the new infrastructure, The accelerator will produce around ten times more collisions over its lifetime than the original LHC and will allow approximately ten times more data to be collected.. What is being changed? Over the next four years, not only a few parts will be replaced. Thousands of engineers and technicians will renew much of the accelerator infrastructure and its experiments.
According to a statement, among the most important improvements are new superconducting magnets capable of much better concentrating proton beams just before they collide. These magnets, cBuilt with niobium-tin technology, they generate much more intense magnetic fields than those used until now and allow the beams to be compressed to extraordinarily small sizes. Special radio frequency cavities, known as crab cavities (crab cavities), which slightly tilt the proton packets before the collision to increase the area of overlap between both beams, thus increasing the number of useful collisions.
Meanwhile, large detectors, such as ATLAS and CMS will be practically rebuilt in many of their components to support an avalanche of data much greater than the current one. New electronic systems, more precise detectors and faster processing algorithms will make it possible to distinguish the really interesting events among millions of collisions every second.
But why is it necessary to generate so many collisions? Because the answers that physics seeks today are extraordinarily elusive. Many hypothetical particles or processes might appear only once in billions of collisions. The more times these conditions are reproduced, the greater the chances of observing extremely rare phenomena. In fact, One of the main objectives will be to study the Higgs boson with a precision never achieved.
Discovering the particle was only the first step. Now physicists want know in enormous detail how it interacts with itself, how it couples to other particles and whether it presents small deviations from the predictions of the Standard Model. Any difference, no matter how minute, could indicate the existence of entirely new physics. The increase in luminosity will also make it possible to investigate very rare processes related to quarks, leptons or particles containing heavy matter, in addition to improving sensitivity in the search for possible candidates for dark matter and other still unknown particles.
But, although the LHC will remain switched off, CERN will be far from idle. In addition to transforming the collider itself, CERN will take advantage of this period to renew a large part of its accelerator complexmodernize experimental facilities, update electrical and security systems and adapt numerous infrastructures for the next decades of research.
Thus, for the next four years the 27-kilometer tunnel located under the border between France and Switzerland will remain without proton beams circulating inside. In its place there will be engineers, welders, technicians, cryogenicists, superconductivity specialists and researchers disassembling, replacing and recalibrating thousands of components. If everything goes as planned, the High-Luminosity LHC will begin operating in 2030. And then a new stage will begin in which the accelerator will not collide protons with more energy than before, but with an intensity never seen before. Something that, paradoxically, will allow us to see much more of the universe around us.